One handle sequence selecting valving for crowd cylinders

ABSTRACT

IN CONNECTION WITH A THREE PART CRANE BOOM HAVING A LIGHTER FORWARD TELESCOPIC BOOM SECTION AND A HEAVIER REARWARD TELESCOPIC BOOM SECTION CONTROLLED BY SEPARATE CROWD CYLINDERS, THE ACTION IS SELECTIVELY CONTROLLED MANUALLY BY A SINGLE HANDLE CONNECTED TO THE VALVES BY A PREFERENCE LINKAGE. MOVING THE HANDLE TO ITS LIMIT IN EITHER DIRECTION WILL EITHER EXTEND OR RETRACTE BOTH CYLINDERS SIMULTANEOUSLY. MOVING THE HANDLE HALF-WAY IN THE CROWD DIRECTION WILL EXTEND ONLY THE CYLINDER FOR THE LARGER INTERMEDIATE SECTION. MOVING THE HANDLE HALFWAY IN THE RETRACTING DIRECTION WILL RETRACT ONLY THE SMALLER FORWARD SECTION. THE PREFERENCE LINKAGE PREVENTS THE WRONG SEQUENCING, I.E., HAVING THE LIGHTER FORWARD BOOM SECTION EXTENDED OUT FROM THE HEAVIER SECTION FIRST, OR MORE THAN THE HEAVIER SECTION IS EXTENDED OUT FROM THE STILL HEAVIER BASE SECTION.

W. J. LADO sept. 2o, uml

ONE HANDLE SEQUENCE SELECTING VALVING FOR CROWD CYLINDERS I5 Sheets-Sheet l Filed Dec.V 22, 1969' W. J. LADC sept. zui 1911 ONE HANDLE SEQUENCE SELECTING VALVING FOR CROWD CYLINDERS Filed Dec. 22, 1969 3 Sheets-Sheet 2 Sept. 20, 1971 w. J. LAno 3,505,551

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United States Patent O 3,605,561 ONE HANDLE SEQUENCE SELECTING VALVING FOR CROWD CYLINDERS William J. Lado, Rome, N.Y., assignor to Pettibone Corporation, Chicago, Ill. Filed Dec. 22, 1969, Ser. No. 887,465 Int. Cl. Fb 15/16 U.S. Cl. 91-413 6 Claims ABSTRACT OF THE DISCLOSURE In connection with a three part crane boom having a lighter forward telescopic boom section and a heavier rearward telescopic boom section controlled by separate crowd cylinders, the action is selectively controlled manually by a single handle connected to the valves by a preference linkage. Moving the handle to its limit in either direction will either extend or retract both cylinders simultaneously. Moving the handle half-way in the crowd direction will extend only the cylinder for the larger intermediate section. Moving the handle halfway in the retracting direction will retract only the smaller forward section. The preference linkage prevents the wrong sequencing, i.e., having the lighter forward boom section extended out from the heavier section lirst, or more than the heavier section is extended out from the still heavier base section.

BACKGROUND AND SUMMARY OF THE INVENTION The invention, of which this disclosure is offered for public dissemination in the event that patent protection is available, relates to control of the telescopic action in crane booms having three or more parts.

IIn three part telescopic booms it is 'very undesirable, or even dangerous, to extend the forward section out of the intermediate section more than the intermediate section is extended out of the base section. The forward section is always of lighter construction than the intermediate section, which in turn is of lighter construction than the base section. The forward section is strong enough for the loads which it is expected to carry when the boom is fully extended, but not for loads to which it could easily be subjected when it alone is extended. This is especially true in connection with mobile cranes on which telescopic booms find their greatest use. These cranes are somewhat limited in their ability to withstand tipping forces, and hence are able to lift much heavier loads close to the wheels than far from the Wheels. This factor provides an automatic safety element protecting the lighter forward section of the boom from being excessively loaded, provided that it is not extended out from the intermediate section more than the intermediate section is extended out from the base section.

Some crane experts believe it 'best that the forward section not be extended at all until the intermediate section is fully extended. 'Ihis gives maximum protection to the forward, lighter section against being overloaded. Other crane experts believe it is best to provide simultaneous or paced extension, the extension of the forward section from the intermediate section keeping pace with the extension of the intermediate section from the base section. The theory here is that this provides adequate protection of the forward section against overloading, while rarely necessitating full extension of the intermediate section from the base section, thus minimizing canting-force problems. The load at the end of the boom tends to produce a canting-force of the intermediate section in the base section. When sections are well retracted one within the other, the canting-forces present no great Patented Sept. 20, 1971 problem because the bearing points for resisting these canting-forces are separated by approximately the amount of the overlap of the two sections. As the sections are extended, however, these bearing points move closer together. At the same time, the leverage arm, repa resented by the extended length of the boom beyond the base section (which necessarily carries the bearing or support point abou-t which the canting-forces act) is increased. Accordingly extremely high forces are exerted on the opposed bearing points resisting the canting action.

Even when the construction is sturdy enough so that there is no danger of breakage or collapse, there is at least increased friction while the sections move with respect to one another in the nearly fully extended position. At the same time, there tends to be a similar problem with respect to the cylinder and piston combination producing the telescopic action. The weight of these parts produces a sagging tendency with canting-forces between the cylinder and the piston-pistonrod assembly, and the bearing points for resisting this canting-force also move closer together as full extension is approached.

There have been various previous inventions and proposals for meeting the problems here discussed. The present applicants prior patent, 3,300,060, disclosed a hydraulic control system for the two crowd cylinders accomplishing the -boom extension which inevitably extended first the cylinder which acted on the intermediate section and inevitably retracted lfirst the cylinder which acted on the forward section. In an application being 'collaterally led by the same applicant, a hydraulic system is used which inevitably extends the two cylinders equally or retracts the two cylinders equally.

According to the present invention, a control system is provided which gives the operator a choice between y equal action of the two cylinders during extension or retraction, or properly sequencing them during extension or retraction, while preventing the improper sequencing in either case. In spite of this option, the control by the operator is exerted through a single control handle.

The means for accomplishment is quite simple. A key feature is the use of a preference linkage between the single handle and two Valves so that for both boom extension and boom retraction one valve has preference and will be the only one actuated if the handle is moved only to the halfway position. This preferred valve, instead of being connected in the usual way with its two cylinder ports (its two control ports) connected to opposite ends of one cylinder is connected to the rear end of one cylinder and to the forward end of the other cylinder. This might seem to present a problem in that heretofore the movement of such a valve in opening the pressure line to one end of the cylinder has also opened the return line from the other end of the cylinder. This problem is solved according to the present invention by using open-neutral valves so that both lines are open to discharge, i.e., to the reservoir, in the neutral position of the valve. Various dangers which this might seem to entail are avoided by placing in each crowd line (the line for each cylinder which leads to its rear or lower end) a pilot actuated check valve which prevents outflow from the cylinder except when predetermined positive pressure is supplied to the line leading to the upper or forward end of the same cylinder.

DESIGNATION OF THE FIGURES FIG. l is a schematic elevational view of a mobile crane having hydraulically extendable and retractable boom sections shown in horizontal, completely retracted position.

FIG. 2 is a similar view with the boom slightly elevated and in partially extended condition.

FIG. 3 is a schematic illustration of a conventional selfcentering control valve of a type which is useful with this invention.

FIGS. 4 through 7 are schematic diagrams showing the cylinders, hydraulic circuits, control valve linkage and manual control handle in accordance with a preferred embodiment of this invention.

FIG. 4 illustrates the condition of the valving when both valves are in open neutral condition.

FIG. 5 illustrates the condition and flow obtained when the control handle moves to the first crowd position.

FIG. 6 illustrates the condition obtained when the control handle is moved to the second crowd position.

FIG. 7 illustrates the condition and ows achieved when the control handle is positioned at its first retrac position.

FIG. 8 represents the conditions and liows obtained when the control handle is positioned at its second retract position.

BACKGROUND DESCRIPTION Mobile crane 20 includes boom supporting superstructure 22, hydraulically extendable boom, generally 24, and boom-elevating cylinder 26. Boom 24 includes three sections, namely main section 28, intermediate section 30 and end section 32. Cable operated lifting mechanism, generally 34, is fixed to the extreme end of end section '32. Section 32 telescopes within middle section 30 and middle section 30 telescopes into main section 28. Sections 30 and 28 must be successively stronger than end section 32 in order to support the lmaximum load, the distances or lever arms being successively longer.

lExtension and retraction of telescoping section 30, 32 is accomplished by means of hydraulic cylinder-piston units, respectively 38, 40, which are similar, although cylinder unit 38 is preferably of greater diameter than cylinder unit 40. Each cylinder unit 38, 40, includes cylinder 44, movable piston 46, piston rod 48, face chamber 50 and rod chamber 52. Cylinder unit 38 includes face charnber conduit connection 54 and rod chamber conduit connection 56. Cylinder unit 40 includes face chamber conduit connection 58 and rod chamber conduit connection 60. Cylinder-end connector 62 and rod-end connector 64 illustrates fastening means by which cylinder 44 and rod 48 are respectively fixed to main boom section 28 and intermediate boom section 30. Cylinder-end connector 66I and rod-end connector -68 schematically illustrate fastening means by which cylinder 44 and rod 48 of cylinder unit 40 are fastened to intermediate boom section 30 and end boom section 32, respectively.

CONTROL VALVES This invention departs from conventional practice especially in its hydraulic circuitry, which may be called criss-cross connection of the cylinders to the valves. The choice of valve and the preferable linkage for operating the valves are related to this hydraulic circuitry.

Valves 70, 72 are both of the spring-centered 3-position, open neutral type, such as Vickers model CM2NO2, illustrated in FIG. 3. Hydraulic fluid under pressure is supplied by pump '75 or 75' through pump lines 77 or 77. Return line 79 carries hydraulic fluid back to a tank or reservoir. Hydraulic conduits 80, 81 are varyingly connected, depending on the position of spool `87. In open neutral position of spool 87 shown in FIG. 3, the return line 79 is open to all the other conduits, so that in effect all four conduits are freely open to one another. Conduits 80, 81 may be considered under substantially 0 pressure. The broken line connection at passage BP recognizes that this passage is connected to line 79 only if no other valve uses the pressure supply.

`Control rod 85 is an extension of valve spool 87. Spring 91 biases cups t93 and 95 against cover-stop 97 and body or stop 99 respectively. Thus movement of rod 85 toward the right hand side of FIG. 3 moves spool 87 and cup 95,

compressing spring 91 until cup 95 strikes cup 93. This movement shifts spool 87 to the position which may be called forward flow. The lands of the spool will now be positioned to shut off passage BP and connect line 81 to pressure line 77 and 80 to return line 79. Upon release of driving force at rod 85, the spring '91 causes cup 95 and spool 87 to shift back to neutral, this movement ceasing when cup 95 strikes stop 99.

When control rod 85 and spool 87 are shifted from neutral to the left, forcing cup 93 to compress spring 91 until the cups come into contact, and the spool is in the reverse flow condition, uid under pressure at conduit 77 is then directed into conduit 80, rather than conduit 81, and lluid in conduit 81 is directed into return line 79. Upon release of the force on rod 85 spring 91 returns cup 93, and spool 87 back to the neutral position illustrated in FIG. 3, i.e., with cup 93 resting against stop 97.

For simplicity of diagramming in FIGS. 4 to 8 the valve ports do not have the same positions as in FIG. 3.

HYDRAULIC CIRCUITS valve) to main cylinder face chamber connection 54. Line 122 of valve 72, which corresponds to line 81 of valve 70 is the retract line for cylinder unit 38, being hydraulically connected (through similar safety valve 125). When pressured lluid is supplied through line '81 it extends cylinder unit 38 and intermediate boom section 30. The return line for oil which must llow from connection 56 at the other end of the cylinder 44 as the piston moves toward it is line 128. Instead of being connected to the same valve 70 according to standard practice, this line criss-crosses to valve 72.

Similarly, the connections of cylinder unit 40 are crisscrossed. Its crowd line 122 (with a similar safety valve 125) is connected to the right hand port of valve 72, ibut its other line is connected to the left-hand port of valve 70.

PREFERENCE LINKAGE Control rods are pivotally secured to bridge 127, a slot 128 or an extra link giving freedom of movement. Master control rod 129 is pivotally secured to bridge 127 at a point which is substantially closer to control rod 85 of valve 70 than to control rod 85 of valve 72, so that portion 130 of bridge 127 is substantially shorter than portion 131. Control handle 132, pivotally mounted to support 13S, is pivotally connected to master control rod 129. In the illustrated embodiment, the straight up and down position of handle 132 represents its open neutral position. Handle positions to the right of open neutral, as viewed in FIG, 3 are crowd control positions and, to the left are retracting control positions, (see FIG. 3). This linkage is a preference linkage causing handle 123 always to operate valve 70 first. Theoretically a preference linkage could have portions 130 and 131 equal if the springs of valve 72 were stitfer than the springs of valve 70. Other preference means could be used, but manual control of cylinder position is desired, to be able to adjust the flow rate.

HYDRAULIC CIRCUIT OPERATION The arrows drawn within the hydraulic system set forth in FIGS. 4 through 8 represent lines of flow within the system. The dotted lines drawn through valves 70, 72 indicate passageways opening to a return line 79 which are available through valves 70, 72 in the position indicated.

Pilot actuated check valves 120, derive their pilot pressures from rod chamber lines 128, 80, respectively and prevent flow out from face chambers 50y in the absence of a substantial threshold pressure in the corresponding rod-chamber hydraulic line, 128, 80. This is a conventional safety feature, but serves a new purpose here. Specifically, it makes possible the use of open neutral Valves, which in turn permit the criss-cross hydraulic connections.

The configuration illustrated in FIG. 4 represents the condition obtained when boom sections 30, 32 are halfway extended and control handle 132 is in the neutral position.

FIGS. 5 and 6 represent the conditions obtained when control handle 132 is moved in successive steps in the crowd direction, i.e., toward the right, as viewed in FIG. 5.

FIGS. 7 and 8 illustrate the conditions obtained when control handle 132 is moved in successive steps in the retrac direction, i.e., toward the left of neutral as viewed in FIG. 3.

Control handle 132 will assume the neutral position, absent substantial urging in either direction, because of the biasing action of spring 91. In this configuration hydraulic lines 81, -128, 122, and 80 are open, through respective valves 70, 72 to a return line 79 which may be thought of as having the O pressure of the reservoir. However pilot actuated check valves 120, 125 prevent ow of uid through lines 81, 122, respectively from face chambers 50, and thus prevent retraction of cylinder rods 148, and telescoping of sections 130, 132 within main section 128. Fluid, under pressure from pumps 75, 75' shunts through valves 70, 72 to return lines 79. Thus, in the neutral condition, the status quo of sections 30, 32 is maintained by check valves 120, 125 and pressurized hydraulic fluid in lines 77 is merely recycled to the tank.

CROWDING Movement of handle 132 in the crowd direction axially shifts master control rod 129 toward valves 70, 72. Movement of master control rod 129 is transmitted to control rods 85 through bridge 127. However, since movement in either direction of control rods 85 is resisted by identical biasing springs 91 and since master control rod 129 is pivotally connected to bridge 127 at a point such that portion 130 is substantially shorter than portion 131 of bridge 127, control rod 85 at the end of short portion 130 will be the first to yield. This shifts spool 87 in valve 70 in the crowd direction, allowing hydraulic liuid in line 77, under pressure from pump 75, to pass through valve 70 as indicated in FIG. 5 into conduit 81 and thence into face chamber 50 of cylinder 44. Valve 125 opens as a simple check valve to flow in this direction. Fluid forced out of rod chamber 52 by the movement of piston 46 in the extension direction passes by way of rod chamber conduit 128 through valve 72 (in open center condition) to return line 79. No change occurs in the status of the other cylinder unit 40 since both of its lines 80 and 122 remain open to a return line 7 9.

When rod 85 of valve 70 reaches the limit of its movement, continued movement of handle 132 must move control rod 85 of valve 72. Hence the condition illustrated in FIG. 6 is obtained, and in this condition, both telescoping sections 30, 32 of the boom 24 are urged toward the extended condition. Valve 72 is now also positioned in the crowd configuration and fluid in line 77', under pressure from pump 75', passes to line 122 and readily passes through check valve 125 into face chamber 50 of cylinder unit 40. Piston 46 of cylinder unit 40 is urged in the extension direction and fluid in rod chamber 52 of cylinder unit 40 passes through rod chamber conduit 80 which is now connected through valve 70 to return line 79 and the tank. Pump 75 for valve 72 may be smaller than pump 75 for valve 70, in proportion to the cylinder cross-actions, so that the speed of extension of the lighter boom section will not be greater than the speed of extension of the heavier section. The piston rod of unit 38 can be larger in diameter so that the retracting speeds will be equal.

The operator wishing to extend boom 24 has the option of moving control handle 132 to the first position illustrated in FIG. 5 to extend only the heavier, middle section 30. He also has the option of moving control handle 132 to the extreme crowd position illustrated in FIG. 6 in which both-the heavier middle section 30 and the lighter end section 32 are extended. Release of handle 132 by the operator automatically causes the return of handle '132 to the'neutral configuration illustrated in FIG. 4 because of the biasing action of springs 91. However, the operator also has the option of manually returning handle 132 initially only half-way to the neutral configuration, i.e., to the position illustrated in FIG. 5, which automatically causes the lighter end section 32 to remain at the status quo, while the heavier middle section 30 continues to extend.

RETRACTING Retraction control conditions are illustrated in FIGS. 7 and 8. Movement of handle 132 in the direction away from valves 70, 72 causes a corresponding shift in the position of master control rod 129. Again, any movement of control rods must be transmitted through bridge 127. However, since bridge portion 130` is substantially smaller in length than bridge portion 131, the difierence in leverage causes springs 91 at valve 70 to yield first so that the configuration illustrated in FIG. 7 is first obtained. In this configuration, spool 87 is shifted to the retract condition so that fluid in line 70, under pressure from pump 75, passes through valve 70 to line 80 and thence into rod chamber 52 of cylinder unit 40 which tends to cause the retraction of the lighter boom section 32. However, pilot actuated valve 125 would prevent this, except that pressure in line 80 actuates pilot check valve 125 permitting fluid from face chamber 50 of cylinder unit 40` to pass by way of hydraulic line 122 through valve 72 to the tank. Since, under these conditions, line 128 is open to return line 79 through valve 72, there is inadequate pressure to the pilot connection of check valve to permit change in the status of heavier, middle cylinder unit 38.

Continued movement of control handle 132 in the "retract direction again shifts master control rod 129 correspondingly. When valve 70 has reached the limit of its movement control rod 129 forces control rod 85 of cylinder 72 outwardly, i.e., to the left as indicated in FIG. 8, bringing valve 72 into the retract configuration also. Since this leads to no change in the connections to end section cylinder unit 40', the discussion of those conditions will not be repeated. However, this does lead to a change in the ow through valve 72. Hydraulic fluid in line 77', under pressure from pump 75', passes through valve 72 into rod chamber line 128, thence intov rod chamber 52 of cylinder unit 38. Generation of pressure in line 128 actuates pilot valve 120 permitting fluid from face chamber 50 of cylinder unit 38 to return by way of hydraulic conduit 81 through valve 70 to the tank.

Again, release of handle 132 by the operator results in automatic return of handle 132 to the neutral posiillustrated in FIG. 4 because of the biasing action of springs 91 at valves 70, and 72. Again, however, the operator can elect to return handle 132 by bringing it first onlyto the configuration shown in FIG. 7 at which point the retraction of the middle section is halted and retraction of the lighter end section is continued.

As to both crowding and retracting handle 132 may be moved all of the way at once, in which case the sequence is so rapid that the beginning of movement of the middle and end sections is apparently simultaneous.

ACHIEVEMENT Using the novel arrangement described hereinbefore, the operator has the option, using only one handle, of extending or retracting the telescoping boom sections, one at a time or both at once, but is prevented from the dangerous operation of extending the light section first or retracting it last.

I claim:

1. In a crane having a three-part telescoping boom, said boom comprising a heavier rearward telescoping section and a lighter forward telescoping section, each of said sections controlled by separate respective crowd cylinders, the improvement comprising:

manual control means for extending and retracting said sections, said control means having a single operator controllable handle, said handle having a neutral position and being movable to a first crowd position and a second crowd position on one side of said neutral position; and to a iirst retract position and a second retract position on the opposite side of said neutral position;

and valve means controllable by said control handle for selectively extending said heavier section when said handle is in the first crowd position, for simultaneously extending both sections when the handle is in the second crowd position, for selectively retracting said smaller section when said handle is in the first retract position, and for simultaneously retracting both sections when said handle is in the second retract position, said control means and valve means being incapable of selectively retracting the heavier section.

2. The improvement of claim 1 in which said valve means comprises two separate self-centering valves, each operable by its respective control rod, and in which said control means includes preference linkage means for connecting said handle to each of said respective rods, and means, responsive to the movement of said handle, for moving one of said rods when said handle is in one of said irst positions, and for moving the other of said rods when the handle is in the second of said operating positions.

3. The improvement of claim 1 in which said valve means comprises two separate valves, each operable by its respective control rod, and in which said control means includes preference linkage means for connecting said handle to each of said respective rods, and means, responsive to the movement of said handle, for moving one of said rods when said handle is in one of said rst positions, and for moving the other of said rods when the handle is in the second of said operating positions, said preference linkage including bridge means pivotally joined at each end to said rods;

respective bias means for urging respective valve means to said open middle neutral position;

connecting rod means for connecting said handle and said bridge means at some point between said attachment of said rods to said bridge, the point of attachment and the relative strength of the bias means having been pre-selected for activation of one valve means upon movement of said handle to either of said first positions, and for activation of both valve means upon movement of said handle to either of said second operating positions.

4. A crane having a boom with base section and intermediate and forward telescopic sections of successively reduced sturdiness, a cylinder unit for each telescopic section for extending and retracting it upon supplying hydraulic fluid respectively through crowd and retraction lines, and a pair of spring-centered reversing valves each having three positions for controlling the supply of hydraulic fluid through said lines, characterized by .a single member operator-controlled for controlling both valves, means responsive to said single member for giving preference to a preferred one of said valves whereby the nonpreferred valve will remain in neutral position except upon further actuation of the single member while the preferred valve is in actuated position;

said lines having criss-cross connections to the valves,

with a crowd line for extending the intermediate section and a retraction line for retracting the end section being connected respectively to the two cylinder ports of the preferred valve, and the crowd lines for the end section and the retraction line for the intermediate section being correspondingly connected to the non-preferred valve; and

said valves being of open neutral type and each supplied with hydraulic fluid from a separate pump.

5. A boom according to claim 4 in which the output capacities of the pumps have substantially the same relationship as the cross-sectional areas of the cylinder units, to provide substantially equal speed of extension of the sections when the single means is fully operated in the crowd direction.

6. ln a crane having a three part telescoping boom, said boom comprising a heavier rearward telescoping section and a lighter forward telescoping section, each of said sections controlled by separate respective crowd cylinders, the improvement comprising:

manual control means for extending and retracting said sections, said control means having a single operator controllable handle, said handle having a neutral position and being movable to a first crowd position and a second crowd position on one side of said neutral position; and to a first retract position and a second retract position on the opposite side of said neutral position;

and valve means controllable by said control handle for connecting two pumps for selectively extending said heavier section when said handle is in the first crowd position, for simultaneously extending both sections when the handle is in the second crowd position for selectively retracting said smaller section when said handle is in therst retract position, and for simultaneously retracting both sections when said handle is in the second retract position, said control means and valve means being incapable of selectively retracting the heavier section; and

the output capacities of the pumps having substantially the same relationship as the elfective cross-sectional areas of the cylinder units, to provide substantially equal speed of extension of the sections when the single means is fully operated in the crowd direction.

References Cited UNITED STATES PATENTS 2,931,340 4/1960 White 91--413X 3,407,951 10/ 1968 Faust et al 9l-413X EDGAR W. GEOGHEGAN, Primary Examiner U.S. Cl. XR.

9l-'4llA; 137-636, 625.69, 596 

